Glossaire · SEO

301 Redirect

A 301 redirect is a server instruction, sent through the HTTP header, that tells browsers and search engines a URL has been permanently moved to a new address. The HTTP 301 status code (Moved Permanently) instructs the crawler to forget the old URL and index the destination instead. It is the canonical tool for preserving rankings during a site migration, a URL structure change, or a page merge: a 301 redirect passes nearly all of the link juice and authority accumulated by the old page on to the new one. Unlike a 302 redirect, which is temporary, the 301 consolidates the ranking signal permanently onto the target URL. Used poorly — redirect chains, loops, or pointing to irrelevant pages — it wastes crawl budget and loses organic traffic that took months to earn.

A 301 redirect is the backbone of any successful SEO migration. When you change a page's URL, remove content, or rebuild a site, it ensures visitors and crawlers land in the right place instead of hitting a 404 error.

How it works

When a browser or Googlebot requests an old URL, the server responds with an HTTP 301 code and the destination address in the Location header. The client is then redirected automatically to the new page. On the search engine side, this signal triggers the transfer of authority — backlinks, age, ranking signals — to the target URL, then the gradual replacement of the old address in the index.

In practice, you configure 301s in the .htaccess file (Apache), the Nginx configuration, or through a CMS's redirect rules. A clean rule points directly to the final destination, never to a URL that is itself redirected.

A concrete example

You migrate site.com/blog/article-2024 to site.com/resources/article. A 301 redirect on the old URL preserves the Google rankings you earned, redirects visitors arriving from an external link, and protects the value of the backlinks pointing to the old page. Without it, you start from scratch.

Key takeaway

Avoid redirect chains (A → B → C). Each hop slows crawling and dilutes the signal. Always redirect A directly to the final target C.

Why it matters

A poorly handled migration can erase months of organic traffic in just days. The 301 redirect is the safety net that protects your organic traffic and your authority. It is also an SEO hygiene lever: it prevents duplicate content by consolidating multiple URL versions (with/without www, HTTP/HTTPS) onto a single canonical address.

FAQ

Questions fréquentes

Yes, in nearly all cases. Google has confirmed that a 301 passes full ranking value, with no loss tied to the status code itself. The losses people observe usually come from redirect chains or poorly matched targets.

A 301 signals a permanent move and consolidates the SEO signal onto the new URL. A 302 signals a temporary move: Google keeps the old URL in its index. For a permanent migration, always use a 301.

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